The present invention relates to methods and apparatus for the pasteurization of egg products utilizing high frequency radio waves. The methods may be used in either batch or continuous pasteurization processes.
Large quantities of liquid egg products are pasteurized each year to produce products sold in refrigerated form with limited shelf life. See generally, Egg Pasteurization Manual (USDA Agricultural Research Service 1969). More recently, the provision of techniques for ultrapasteurizing liquid egg products has led to the marketing of liquid egg products which have extended shelf lives under refrigerated conditions.
Methods of ultrapasteurizing liquid whole egg products using indirect heat, such as contacting the liquid whole egg product to a heated surface, or direct heat, such as contact to or the injection of steam, are known. See U.S. Pat. Nos. 4,808,425 to Swartzel et al.; 5,105,724 to Swartzel and Ball; and 4,957,760 to Swartzel et al.
U.S. Pat. No. 4,091,119 to Bach discloses a method and apparatus for uniform heating of a foodstuff for preservation using high-frequency electromagnetic fields. The foodstuff (in particular, a jam, marmalade or jelly) is located in a container open at its top, and two fields, one high frequency and another ultra-high frequency, are directed as different portions of the foodstuff container. Use of a high frequency field of between 1-300 MHz, used in conjunction with an ultra-high frequency field of between 300 MHz and 5 GHz, is disclosed.
U.S. Pat. No. 4,853,238 to Huang discloses a method for treating liquid egg white or liquid whole egg in order to extend the shelf-life of the liquid egg material. The liquid egg material is subjected to microwave energy while it flows in a conduit for a time sufficient to inactivate or destroy a sufficient amount of microorganisms in the material without significantly reducing the egg protein functionality of the material.
U.S. Pat. No. 4,975,246 to Charm discloses a method and apparatus for pasteurizing and/or sterilizing heat-sensitive material using. high-temperature, short-time heating to substantially destroy selected microorganisms without substantially affecting other desirable properties of the material. Heat-sensitive material, such as liquid egg product, is continually passed through a flow path, such as plastic tubing, subjected to microwave radiation to heat the material to a high temperature for a short period, and then rapidly cooled.
Disclosed is a method of pasteurizing a flowable egg product in a continuous flow apparatus. The method comprises the steps of: (a) passing a flowable egg product continuously through a conduit transparent to high frequency radio waves; (b) heating the flowable egg product to a predetermined temperature by subjecting it to high frequency radio waves; and then (c) holding the flowable egg product at said predetermined temperature for a predetermined time; wherein the total thermal treatment of the product is sufficient to pasteurize the product. Preferably, the total thermal treatment is sufficient to achieve a five, six, seven or even nine log cycle reduction in Listeria monocytogenes without significantly reducing the egg functionality.
An apparatus for pasteurizing a flowable egg product is also disclosed. The apparatus comprises: (a) an egg product holding tank; (b) an egg product line connected to the holding tank; (c) pumping means connected to the egg product line for establishing an egg product stream in the egg product line; (d) a radiolucent conduit interposed in the egg product line; (e) a generator capable of generating high frequency radio waves and placed so that radio waves generated pass through the radiolucent conduit to heat the egg product stream; and (f) a holding section in the egg product line after the radiolucent conduit.
Also disclosed is a method of pasteurizing a flowable egg product comprising the steps of: (a) heating the flowable egg product to a predetermined temperature by subjecting it to high frequency radio waves; and then (b) holding the flowable egg product at said predetermined temperature for a predetermined time; wherein the total thermal treatment of the product is sufficient to pasteurize the product. Preferably, the total thermal treatment is sufficient to achieve a five, six, seven or even nine log cycle reduction in Listeria monocytogenes without significantly reducing the egg functionality.
An apparatus for pasteurizing an egg product is also disclosed. The apparatus comprises: (a) egg product holding means; (b) a generator capable of generating high frequency radio waves and operatively associated with said egg product holding means and positioned so that radio waves generated heat egg product contained within the egg product holding means.
Another apparatus for pasteurizing egg products is disclosed, comprising (a) conveying means for transporting an egg product along a predetermined product path; (b) a generator for generating high frequency radio waves, the generator operatively associated with the conveying means and positioned so that an egg product conveyed on the conveying means is exposed to high frequency radio waves generated by said generator; and (c) holding means for holding the egg product for a predetermined time, the holding means operably connected to the conveying means for receiving the egg products.
Radio frequency energy has been reported as being used to scramble eggs (See, e.g., xe2x80x9cMagna-Tubexe2x80x9d heat processing equipment sales brochure, Proctor Strayfield, Horsham, Pa.), but has not heretofore been suggested for use in pasteurizing egg. Advantages of high frequency radio waves for egg pasteurization include, among other things, the uniformity of heating provided thereby, the avoidance of adding water to the product such as by steam injection, and the avoidance of fouling of heated surfaces.
The foregoing and other objects and aspects of the present invention are explained in detail in the specification set forth below.